He told NPR radio: "The commercial shows on television that have amateur contests on singing or performing - there's a big accent on same.

"You should think more of longevity and know that it takes years to really become a good performer.

"And performers should really go to the best schools, like Lady Gaga, you know, she went to New York University (NYU) and had great teachers.

"It's best to really study your technique as much as you possibly can so you can have a long career instead of a quick one that's a failure."

The 86-year-old star hasn't relaxed in his old age and practices vocal warm ups and exercises every day to keep him sounding at his best.

He added: "It's based on the vowel sounds A, E, I, O, and by doing that, you just warm up. Because every day you really feel quite different.

"By doing the scales, you get a center, and all of the sudden you feel in control of your voice, where it's relaxed. And it takes about 10 or 15 minutes.

"I don't sing operatically, and I sing very intimately, but I still do the scales, and I think in terms of intonation and making sure that I'm hitting the notes right on the head and having it appear quite effortless."